This is the starting point for a lightweight build for my fiance. Built the frame to fit her and it ended up being roughly a 51 cm frame. Built up with the best components I could afford at the moment, it still weighs a not too bad 7.68 kg (16.94 lbs) which considering it's a steel custom frame. There's still plenty of room for improvement which will happen a little while down the road when I build the carbon version of this frame for her and start my new job at Praxis (convenient source of parts. . .).

I am also curious about the weight of the frame. I forgot to weigh it before I built up the bike. I'll be stripping everything off before it goes to paint so I will update with a frame weight then.

As far as how I would make a composite version of this bike, I have two options on how to do that. The first is to do it the way English does and use the steel as lugs and replace tubes with carbon. It's the easier way to do it and will most likely be an intermediate step. The more difficult way of doing it would be to machine some bladder compression molded parts for the frame and then bond them together as is the industry standard. I would have to make some interesting parts in order to keep the twin top tube but I think it would definitely still be possible.

As far as the recumbent in the background goes, that's a weight weenie of a different sort. I'm the team lead of the Human Powered Vehicle team this year at Cal Poly SLO and we built that bike fully out of composites in order to drop the weight from the usual 60-70 pounds that these bikes weigh down to 48 lbs. Not light by diamond frame standards but we still built ourselves a pretty sweet carbon frame for that one. Bladder compression molded joints and the like. The weight of that frame was 2.4 kg which we are planning on dropping lower for next year as we had a fillet brazed steel lug in there instead of all composite which just about doubled the weight of the frame.

If y'all are interested I can post more details in a separate thread. I just figured recumbents wouldn't be of interest to people here.

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